Ordnance Department. 9-421. 3-inch seacoast gun matériel. 3-inch (15-pdr.) gun M1902M1 mounted on 3-inch (15-pdr.) barbette carriage M1902, and 3-inch (15-pdr.) gun M1903 mounted on 3-inch (15-pdr.) barbette carriage M1903 [with list of references], Oct. 10, 1942; [prepared under direction of chief of ordnance].